What to do first when the application encounters an error

January 5, 2026 2 min read

short-postbase-knowledgedebugging

Question:

What do you do first when the application encounters an error? (Testing debugging ability and logical thinking.)

First, I log the application’s execution flow to figure out which block contains the error.
I divide the code into blocks and check them one by one. For example, if I have 3 blocks and 2 are correct, the bug is probably in the remaining one.
After I find the faulty block, I add more detailed logs. When the app runs, those logs show how the code moves step by step, which makes it easier to spot where the logic goes wrong.
This helps me narrow down the bug. It could be a logic error or a race condition, where two blocks run in parallel and one finishes earlier than expected.

Things to avoid when debugging:

Reading the entire codebase at once. That makes it easier to miss small, hard-to-spot errors and gets tiring fast.
Relying on theories that are really just unverified guesses.
Fixing errors immediately without understanding the original bug, which can create new ones.
Not logging. If you do that, you lose visibility into how the code actually runs.